The present invention relates to novel coumarin derivatives and their salts, and further to a process for the preparation thereof and a pharmaceutical composition containing the coumarin derivatives.
It is known that a certain kind of coumarin derivatives have an antiallergic activity. For instance, Japanese Patent Unexamined Publication No. 64273/1975 discloses that coumarin compounds of the general formula (I): ##STR2## wherein X is an alkyl group or an aryl group, X.sup.1, X.sup.2, X.sup.3 and X.sup.4 are the same or different and each is hydrogen atom, nitro group, an alkyl group, an alkoxyl group, an aryl group, an aralkyl group, a heterocyclic group, a halogen atom, carboxyl group or an acyloxyl group, and any adjacent two groups of X.sup.1, X.sup.2, X.sup.3 and X.sup.4 may form a substituted or unsubstituted condensed carbon or heterocyclic ring with the carbon atoms bonding thereto, show an antiallergic action. However, these coumarin derivatives (I) are not always satisfactory antiallergic agents.